Corn milling test



Patented Apr. 15, 1952 UNITED STATES PATENT OFFICE CORN MILLING TEST Majel M. MacMasters, Peggy Baird, and Carl E. Rist, Peoria, 111., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application March 14, 1951, Serial No. 215,620

3Claims. (Cl.73-432) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention herein described may be manucorn, but for many reasons a tendency to use too factured and used by or for the Government of high temperatures, both on the farm and at elethe United States of America for government l vators persists. The use of too high temperatures purposes throughout the world without the pay results in heat-damaged corn, undesirable for ment to us of any royalty thereon. 5 the production of starch or for processing by dry This invention relates to a novel method of milling. Corn dried at temperatures above apcontrol and assay of corn, particularly in conproximately 130 F. gives harder grits and more junction with subsequent milling processes inrubbery germ than that dried at lower temperavolving the corn. More particularly, the inventures. There is also a marked tendency for oil tion relates to a method for determining the millto be found in starch separated from the overability of corn whereby corn unsuitable for millheated corn. ing purposes can be detected by a novel and rapid Freezing, as well as overheating, may likewise test. result in damaged corn, if the moisture content A major proportion of corn from farms in this of the corn is relatively high, for example, corn country, finding its way into industrial chancontaining more than about 23 percent moisture nels, goes into the wet milling and dry milling after being frozen under conditions prevailing in industries. In these industries, starch, corn profarm and elevator storage.

tein, corn oil, meal, special feed and feed concen- We have found a close correlation between the trates and industrially processed cereal foods millability of corn and the viability of the corn are produced. germ. This is particularly true of mature corn The products of the corn milling industry repthat has been killed by heat or by natural freezresent a considerable volume of the staple trade ing. We have, moreover, discovered that a speand commerce of the land. Modern corn milling cific viability test hereafter to be described, is of utilizes a maximum of scientific methods and great value in predetermining the suitability of scientifically designed equipment, reducing wast- 25 corn for milling. Our test is rapid and can be age to a minimum, and producing the wide vaused with simple equipment in the field, or at riety of industrially important products previouscorn trading centers. 1y mentioned. The viability test with 2,3,5-triphenyltetrazoli In recent years, however, corn millers have um chloride, developed by Lakon (Plant Physiol. encountered increasingly diificult problems in 24: 389-394) involves the production of an easmilling corn harvested and processed by current ily discerned carmine-red color in living portions agricultural and storage equipment. Conseof the germs of seeds. As carried out by prior quently, corn millers are experiencing an inten- Workers, this test requires a total of 7-18 hours. sifying need for a rapid test to determine, be- We have modified the test so that the total time fore purchase, the suitability of corn for their required can be reduced to a maximum of 4 hours use. Unsuitable corn may then be diverted to and, in actual practice, can give a s ti fa t r other more suitable uses with a consonant savingtest for millability in about 1 hour. Employing f v luabl food m t i l d y, I the our modification, this test, according to our inpast few years, this need has grown as the result vention is applied advantageously previous to and of the increasingly prevalent practice of drying in conjunction with milling, either wet or dry, as corn artificially. Several factors have contriban excellent predetermination of the millability uted to make artificial drying an increasingly of the corn. The stained kernels may be dried common practice, chief of which is the present and stored as a record of the viabi ty widespread use of mechanical corn pickers. Har- According to our invention, corn, p us to vest with a corn picker is completed in about onemilling, is p ed nd e sample usually third, or less, the length of time formerly required tened by soaking in water. After soaking, each for hand picking. Hence much of the corn has kernel to be tested is bisected longitudinally per-' less time to dry in the field. pendicular to the broad face. The cut may be The United States Department of Agriculture made with any sharp instrument, for example, a has recommended proper procedure for drying razorblade, if desired, while the kernel is held under water. One-half of each kernel is laid, out side down, in a container, i. e., dish, containing sufdcient aqueous triphenyltetrazolium chloride solution to cover the kernel pieces. The dish may then be placed in a dark region for a period up to one and one-half hours or longer. The period sufficient for the purposes of this invention need not exceed 2 hours.

The concentration of the triphenyltetrazolium chloride solution should be at least 0.5 percent, preferably about 1.0 percent. The upper limit of concentration is not critical. A broad and rather definitive test of viability and milling quality maybe made, if desired, by using a staining time of one and one-half hours or more and counting as acceptable for milling those sample kernels which exhibit a pink to carmine-red coloration of at least the plumule and mesocotyl region, including the adventitious root buds, and

the entire midsection of the scutellum of the kernel pieces with the reagent can be limited to about 30 minutes. In this case, those pieces showing a pink color over the entire cut surface of the germ are counted as viable.

A close estimate of the viability of corn, sufficient for most practical purposes, can be madewith triphenyltetrazolium chloride in one hour or less. The corn is bisected without the preliminary soaking, and the viability is determined after a 30-minute to l-hr. staining period, the coloration being a pink to carmine-red.

Certain precautions should be observed in applying the test. For example, there may be some mechanical diificulty in bisec'ting the hard kernel if the accelerated test is employed. The resulting damage to the cells sometimes causes a heavy scum which must be removed before the test.

Care must be taken in bisecting the kernels in order to insure cutting through the upper portion of the embryonic plant. The surfaces of tissues not bisected do not readily take up the reagent, and a proper interpretation of the test is difficult. In testing corn heavily contaminated with bacteria, a colored deposit may form over the cut surface. This deposit need not interfere with the test, however; and it can be scraped away before the kernel i examined. The reagent solution is sensitive to light, but it can be kept for several months in a dark bottle stored in a cool place. It is light amber when prepared, and the appearance of a dark amber color indicates that it is no longer useful.

Corn, which has previously been frozen, often gives a purplish-red color, rather than the usual carmine-red. This indicates that the germ, if not already non-viable, is in the process of dying.

The following specific examples illustrate the invention.

EXAMPLE 1 Six samples of naturally soft, shelled corn, not moldy, containing from 18.6 to 30.3 percent moisture were dried immediately upon receipt at temperatures varying over 10 intervals from 110 to 220 F. For drying, the corn was placed in l x x 5-inch containers made of /.;,-inch wire cloth. The containers were filled with corn and 4 placed in a forced-draft oven maintained at the required temperature. The samples were dried to approximately 13 percent moisture content.

One sample was also obtained after commercial drying, and one which had been dried artiflcally on a farm.

After drying, the kernels were soaked for one hour in distilled water, out longitudinally perpendicular to the broad face and placed in a Petri dish containing 1 percent triphenyltetraaolium chloride. The dish was then placed in a dark cabinet at room temperature for 1 hour. The kernel pieces'were then examined to determine viability. The difference between results obtained on samples of the same corn by standard germination test and the triphenyltetrazolium chloride test was within the 5 percent range. As determined by the latter test, the samples were designated viable or non-viable, as tabulated in Table I.

Table I Percent Germination Sample No. Triphenylterglzoliim igg g on e Method Method EXAMPLE 2 Six samples of yellow dent corn, harvested at varying stages of maturity and kiln dried at various temperatures were subjected to viability tests in the same manner as those of the foregoing example. These samples were then wet milled by the following procedure.

Four hundred grams (weight, as received) of each sample were placed in a 2-liter Erlenmeyer flask with bottom drawn to form an inverted cone, and steeped for 6 hours at 49 C. in 1,000 ml. of a circulating aqueous steep solution containing 0.05 percent S02. Starting at the end of 6 hours, a 0.2 S02 solution was slowly fed into the steeping flask at a rate of 1,000 ml. per 18 hours. To maintain a constant volume, an equal amount of steeping solution was removed from the flask by a siphon system.

At the end of the 24-hr. steeping period-the steeped solution was drained off and the corn was ground, and then sieved through a 200-mesh copper screen. The separated fiber was mixed with water and ground twice more, and the ground slurry screened to separate the starch and gluten from the fiber. The fiber was washed, and the screened washings added to the combined slurries. The gluten and starch were separated by a series of centrifuge cycles constituting shaking, centrifuging, decanting, and removing the gluten layer. The recovered starch was dried to about 12 percent moisture in a forced draft oven at 40 In Table II, the results of the above procedure are summarized. Samples No. 7-9 are those possessing satisfactory milling characteristics. Whereas, samples No. 10-12, showing negative viability tests, also exhibit unsatisfactory milling characteristics in low starch recovery, excessive protein in thestarch, or both.

Table II v 4 P z Drying 13 y omen Percent Sample No. Tempera T I Starch ture F. r p my m are Recovery tetrazollum (N X625) Chloride 110 a l 0. as 77 75 as 0. 25 79 124 82 0. 38 79 150 0 O. 69 63 181 0 0. 31 6-5 183 Q 0. s1 s7 The foregoing data illustratethe close correlation between our triphenyltetrazblium chloride test and the wet millability of the'corn. A similar correlation exists for thecorn when subsequently processed by dry milling.

We claim:

1. In the process of treating acorn by industrial milling processes, the step which comprises subjecting a representative sampleofiseed corn to a millability test comprising bisecting by cutting kernels of seed corn longitudinally perpendicular to the broad face of the kernels and exposing the cut surface of the kernels to an :aqueous solution of 2,3,5-triphenyltetrazolium chloride for to 2 hours, whereby millabillty of said sample is indicated by the appearance of a, pink to carminered coloration of at least the pluihule and mesocotylregion, including the adventitous root buds, and the entire midsection of the scutellum of said gem;

2, Process of claim 1 in which the kernels are softened in water prior to cutting.

[3; The method which comprises cutting corn kernels longitudinally perpendicular to the broad face and subjecting the cut surfaces to the action of an? aqueous solution of 2,3,fi -triphenyltetrazoliurnchloride for approximately} hour, whereby viability and millability of said corn is indicated bythe appearance of a pink "to carmine-red coloration of at least the pluinule and mesocotyl region, including the adventitious root buds, and the entire midsection of the scutellum of said germ. MAJEL MgMACMASTERS.

PEGGY BAIRD.

CARL nfmsT.

REFERENCES crrnn following references are of record. in the file of this patent:

UNITED STATES PATENTS 

1. IN THE PROCESS OF TREATING CORN BY INDUSTRIAL MILLING PROCESSES, THE STEP WHICH COMPRISES SUBJECTING A REPRESENTATIVE SAMPLE OF SEED CORN TO A MILLABILITY TEST COMPRISING BISECTING BY CUTTING KERNELS OF SEED CORN LONGITUDINALY PERPENDICULAR TO THE BROAD FACE OF THE KERNELS AND EXPOSING THE CUT SURFACE OF THE KERNELS TO AN AQUEOUS SOLUTION OF 2,3,5-TRIPHENYLTETRAZOLIUM CHLORIDE FOR 1/2 TO 2 HOURS, WHEREBY MILLABILITY OF SAID SAMPLE IS INDICATED BY THE APPEARANCE OF A PINK TO CARMINERED COLORATION OF AT LEAST THE PLUMULE AND MESOCOTYL REGION, INCLUDING THE ADVENTITOUS ROOT BUDS, AND THE ENTIRE MIDSECTION OF THE SCUTELLUM OF SAID GERM. 